PHP recursively implements a function to generate drop-down lists by infinite categories_PHP Tutorial

/*—————————————————— * /
//– Recursive implementation of infinite classification generation drop-down list function
//– $tpl->assign('sort_list',createSortOptions ());
//– $tpl->assign( 'sort_list',createSortOptions ($sort_id));
/*—————————————————————— */
function createSortOptions ($selected=0,$parent_id= 0,$n=-1)
{
global $db;
$sql = "SELECT * FROM `@__article_sort` WHERE `parent_id` = '{$parent_id}'";
$ options = ";
static $i = 0;
if ($i == 0)
{
$options .= 'if ($row['sort_id'] == $selected)
{
$options .=' selected ';
}
$options .=">".str_repeat(' ',$n*3).$row['sort_name']."n";
$options .=createSortOptions ($selected,$row['sort_id'],$n);
}
}
return $options;
}